Aziridine n-carboxylates



United States Patent 3,544,559 AZIRIDINE N -CARBOXYLATES Hiroshi Tanida, Osaka, and Teruji Tsuji, Takatsuki-shi, Japan, assignors to Shionogi & Co. Ltd., Osaka, Japan No Drawing. Original application Oct. 27, 1965, Ser. No. 505,400, new Patent No. 3,445,456, dated May 20, 1969. Divided and this application Sept. 18, 1968, Ser.

Int. Cl. C07d 23/06 U.S. Cl. 260-239 4 Claims ABSTRACT OF THE DISCLOSURE Compounds of the formula:

Rooor/ on2 I wherein the symbol represents hydrogen atoms at the 5- and 6-positions, a double bond between the 5- and 6-positions or a condensed benzene ring with or without one or more substituents between the 5- and 6-positions.

Accordingly, it is a basic object of the present invention to embody the norbornenyl aziridine compounds (I). Another object of this invention is to embody the norbornenyl aziridine compounds (I) useful as antidepressants and psychomotor stimulants. A further object of the invention is to embody a process for preparing the norbornenyl aziridine compounds (I). These and other objects will be apparent to those conversant with the art to which the present invention pertains from the subsequent description.

The present invention comprises subjecting a norbornenyl compound represented by the formula:

wherein R represents a lower alkyl group, an aryl group Patented Dec. 1, 1970 ICC or an at (lower) alkyl group to give a triazoline compound represented by the formula:

OOOR

ROOON 1 pm wherein R has the same significance as designated above and wherein the symbol has the previously indicated significance and eliminating the N-substituent from the N-substituted aziridine compound (IV) to give the corresponding aziridine compound (I).

The heretofore-known synthetic method for the production of this type of aziridine derivative involves irradiating an azide compound with ultra-violet light to give a nitrine, and thereafter treating the resultant nitrine with an olefine [W. Lwowski et al.: J.A.C.S., Vol 85, p. 1200,

1963]. When this method is applied to a norbornenyl compound, yield-impairing various side reactions tend to occur. The present inventors have found that an aziridine compound (I) can be prepared in a good yield by react ing the corresponding norbornenyl compound (II) with an azidoformate to give the triazoline compound (III), decomposing the triazoline compound (III) to give the N-substituted aziridine compound (IV) and thereafter eliminating the substituent at the N-position from the N- substituted aziridine compound. Since such a decomposition reaction of a triazoline has heretofore been eitected by heating the triazoline compound in a solvent of high boiling point, there have inevitably been involved various undesirable side reactions conducive to a poor yield [K. Alder et al.: Liebigs Ann. Chem., vol. 501, p. l, 1933]. However, it has been found by the present inventors that an N-substituted aziridine compound can be obtained in a high yield by decomposing the triazoline compound in a low-boiling solvent.

Examples of starting materials employed in the present process are 2-norbornene, 2,5-norbornadiene and substituted or unsubstituted benzo[5,6]-2,5-norbornadiene. As substituents possibly present on the benzene ring, there are exemplified lower alkyl group (e.g., methyl, ethyl, propyl), lower alkoXy group (e.g., methoxy, ethoXy, propoxy), halogen (e.g., chlorine, bromine, iodine), amino group, (lower)-alkylamino group (e.g., methylamino, ethylamino), di(lower)alkylamino group (e.g., dimethylamino, diethylamino) and cyano group.

The present process comprises three steps, that is, [A] reacting the starting material (II) with an azidoformate to give the triazoline compound (III), [B] decomposing the triazoline compound to give the N-substituted aziridine compound (IV) and [C] eliminating the substitutent at the N-position from the N-substituted aziridine compound to give the objective aziridine compound (I).

A STEP phenyl azidoformate, p-nitrophenyl azidoformate) or ar- (lower)alkyl azidoformate (e.g., benzyl azidoformate, phenethyl azidoformate) in an inert solvent. As the inert solvent, there are exemplified hydrocarbons such as benzene, toluene, xylene, hexane or pentane, petroleum solvents such as petroleum ether or petroleum benzine, and halogenated hydrocarbon such as carbon tetrachloride. The present reaction proceeds smoothly under cooling or at room temperature. Since the azide compound is sensitive to light or heat and therefore a radical reaction may occur, the present reaction is favorably carried out in a cool and dark place. Thus, the triazoline compound (III) is prepared in a high yield.

B STEP Next, the triazoline compound (III) is treated with a lower alkanol such as methanol, ethanol or butanol at room temperature or under slight heating to give the N- substituted aziridine compound (IV) together with generation of nitrogen gas.

C STEP Further, the N-substituted aziridine compound (IV) is hydrolyzed for eliminating the substituent at the N-position to give the objective aziridine compound (I). As methods of hydrolysis, there are exemplified a method of treatment with alkali hydroxide such as sodium hydroxide or potassium hydroxide in per se conventional manner and a method of treatment with a metallic hydride complex such as lithium aluminum hydride and decomposing the produced metallic complex with water.

The thus-obtained aziridine derivatives (1) can be, when required, converted into acid addition salts such as acetate, oxalate, succinate, picrate, salicylate, carbonate or malate, etc. in per se conventional manner.

There may be produced steric isomers of the aziridine (i.e., endo type and exo type) in the objective substances, but these are all comprised in the present invention.

The objective aziridine compounds (I) are useful as antidepressants and psychomotor stimulants. For instance, 2,3-exo-imino-benzo[5,6]-5-norbornene controls ptosis in rats induced by subcutaneous administration of milligrams of reserpine per kilogram of body weight, when previously administered by subcutaneous route at a dose of 25 milligrams per kilogram of body weight. Further, the previous administration of 10 milligrams of the said compound per kilogram of body weight by intravenous route increases blood pressure elevation in urethan and phenobarbital sodium-anesthetized cats caused :by intravenous administration of 10- milligrams of noradrenaline per kilogram of body weight. The previous administration of 50 milligrams of the said compound per kilogram of body weight by subcutaneous route increases spontaneous motor action moderately for 110 minutes. The previous administration of 25 milligrams of the said compound per kilogram of body weight by subcutaneous route potentiates narcosis for 6 minutes and 36 seconds in anesthetized mice caused by subcutaneous administration of 35 milligrams of thiopental sodium per kilogram of body weight in comparison with that of the control (thiopental sodium) for 3 minutes and 40 seconds. Furthermore, the said compound protects mice from tonic extensor induced by electroconvulsive shock, when given at the 50 percent effective dose (ED 61.7 milligrams per kilogram of body weight. The acute toxicity (LD of the said compound in mice is as follows: subcutaneous 578.4 milligrams per kilogram of body weight.

Presently preferred and practical embodiments of the present invention are illustratively shown by the following examples. In these examples, the relationship of parts by weight to parts by volume is the same as that between grams and milliliters. Temperatures are set forth in degrees centigrade.

4 EXAMPLE 1 (a) To pentane (50 parts by volume), there are added 'benzo[5,6]-2,5-norbornadiene (27.4 parts by weight) and ethyl azidoformate (20 parts by weight), and the resultant mixture is allowed to stand in a cool and dark place for a week. The precipitated crystals are collected by filtration, washed with pentane and the crude product (38.4 parts by Weight) is recrystallized from ether to give 3a,4,9,'9a tetrahydro-l-carboethoxy 4,9 methanonaphtho[2,3-d]triazole as cubic crystals melting at 94 C.

(b) A solution of 3a,4,9,9a-tetrahydro-l-carboethoxy- 4,9-methanonaphtho[3-d]triazole (29.9 parts by Weight) in anhydrous methanol is warmed at 40 C. to lead to vigorous bubble formation and decomposition. Warming is continued for about 2.5 hours and the methanol is evaporated under reduced pressure. The residue is distilled at 130 C./mm. Hg to give 2,3-exo-carboethoxyimino-benzo[5,6]-5-norbornene (25.2. parts by weight).

(c) A solution of 2,3-exo-carboethoxyimino-benzo-[5, 6]-5-norbornene (11.6 parts by weight) and potassium hydroxide (5.5 parts by weight) in ethanol (250 parts by volume) is refluxed for 4 hours. The solvent is evaporated under reduced pressure. The residue is combined with Water and the mixture is shaken with ether. The ethereal layer is dried over potassium carbonate and the ether is evaporated to give 2,3-exo-imino-benzo[5,6]-5-norbornene 5.9 parts by weight) as crystals melting at 95 to 96 C.

EXAMPLE 2 (a) To pentane (200 parts by volume), there are added 2-norbornene (47.43 parts by weight) and ethyl azido formate (43.5 parts by weight), and the resultant mixture is allowed to stand in a cool and dark place for a week. The reaction mixture is concentrated under reduced pressure at 50 C. to give 3a,4,5,6,7,7a-hexahydro-l-carboethoxy-4,7-methanobenzotriazole (75.66 parts by weight) as an 02.

(b) A solution of the above triazole (75.66 parts by weight) in anhydrous methanol is warmed at 39 to 41 C. to lead to vigorous bubbling and decomposition. Warming is continued for about 2.5 hours and the methanol is evaporated under reduced pressure. The residue is distilled at 75 to 76 C./3 mm. Hg to give 2,3-exo-carboethoxyimino-norbornane (56.7 parts by weight).

(0) A solution of 2,3-exo-carboethoxyimino-norbornane (6.30 parts by weight) and potassium hydroxide (3.91 parts by weight) in alcohol (200 parts by volume) is refluxed for 4 hours. The solvent is evaporated under reduced pressure. The residue is combined with water and the mixture is shaken with ether. The ethereal layer is dried over anhydrous potassium carbonate and the ether is evaporated. The residue is sublimed at 80 C./ 10 mm. Hg to give 2,3-exo-imino-norbornane. This substance is unstable and readily forms its carbonate in the atmosphere. Its oxalate melts at 138 to 139 C.

EXAMPLE 3 (a) To pentane (200 parts by volume), there are added 2,5-norbornadiene parts by weight) and ethyl azidoformate (48.1 parts by weight) and the resultant mixture is allowed to stand for 4 days. The reaction mixture is concentrated under reduced pressure at 50 C. to give crude crystals. The crude crystals are recrystallized from hexane to give 3a,4,7,7a-tetrahydro-1-carboethoxy-4,7- methanobenzotriazole (63 parts by weight) as cubic crystals melting at 66 to 67 C.

(b) A solution of 3a,4,7,7a-tetrahydro-l-carboethoxy- 4,7-methano-benzotriazole (50.9 parts by weight) in anhydrous methanol is warmed at 39 to 41 C. to lead to vigorous bubbling and decomposition. Warming is continued for about 2.5 hours and the methanol is evaporated. The residue is distilled at 80 C. to 82 C./ 4 mm. Hg to give 2,3-exo-carboethoxyimino-5-norbornene (26.4 parts by weight).

(0) A solution of 2,3-exo-carboethoxyimino-S-norbornene (5.0 parts by weight) and potassium hydroxide (2.35 parts by weight) in ethanol (200 parts by volume) is refluxed for 8 hours, and the resultant mixture is concentrated under reduced pressure. The residue is combined with water and the mixture is shaken with ether. The ethereal layer is dried over anhydrous potassium carbonate and the ether is evaporated. The residue is distilled at 120 to 130 C./2 mm. Hg (bath temperature) to give 2,3-exo-imino-5-norbornene (1.8 parts by weight). This substance is quite hygroscopic and decomposes in the atmosphere. Its oxalate, acetate and picrate readily decompose.

What is claimed is:

1. A compound of the formula:

2 1 s ROCON/ JH2 wherein the symbol represents hydrogen atoms at positions 5- and 6-, a double bond between said positions or a condensed benzene ring which is unsubstituted or substituted with at least one substituent selected from the group consisting of lower alkyl, lower alkoxy, halogen, amino, loweralkylamino, di(lower) alkylamino and cyano.

2. A compound according to claim 1, said compound being the 2,3-exo-carboethoxyimino-benzo[5,6]-5-norbornene.

3. A compound according to claim 1, said compound being the 2,3-exo-carboethoxyiminonorbornane.

4. A compound according to claim 1, said compound being the 2,3-exo-carboethoxyimino-S-norbornene.

References Cited UNITED STATES PATENTS 3,284,444 11/1966 Franz 260-239 ALTON D. ROLLINS, Primary Examiner US. Cl. X.R. 424-244 

